Information recording medium and methods of manufacturing and using the same

ABSTRACT

An information recording layer on a substrate provides a method of recording information by selectively opening the rings of dicyclopentadiene skeletons, thus recording information by forming cyclopentadiene skeletons. The information recorded by the method can be erased by the cycloaddition of cyclopentadiene skeletons. Information can also be recorded or erased by incorporating or eliminating a metal ion from a selectively opened section of a ring of a dicyclopentadiene skeleton after forming an organic thin film comprising the dicyclopentadiene skeleton. Alternatively, after the formation of an organic thin film comprising a cyclopentadiene skeleton, a heterocycle or a benzene ring, a metal ion is incorporated or eliminated from a section between at least two rings of the cyclopentadiene skeleton, the heterocycle or the benzene ring. Thereafter, a metallocene skeleton or a skeleton analogous to the metallocene skeleton is formed or eliminated, thus recording or erasing information. The selective opening of a section of a dicyclopentadiene skeleton ring is carried out by heat or light. The readout of the information is performed by recognizing the cyclopentadiene skeleton, the metallocene skeleton, the skeleton analogous to the metallocene skeleton or the metal atom. The information recording layer of the invention is a chemically adsorbed monomolecular film with a thickness at the angstrom level.

This application is a division of U.S. application Ser. No. 08/453,506filed May 30, 1995; now U.S. Pat. No. 5,591,487, which is is a divisionof U.S. application Ser. No. 107,308, filed Aug. 17, 1993, now U.S. Pat.No. 5,447,778.

FIELD OF THE INVENTION

The invention relates to an information recording medium and a method ofmanufacturing the same, and to methods of reading and erasing recordedinformation on the information recording medium.

BACKGROUND OF THE INVENTION

Conventional information recording media include thin inorganic magneticmaterials used for magnetic recording or photoelectromagnetic recording,organic photoisomerization materials used for optical storage, and thelike.

Furthermore, Langmuir-Blodgett (LB) films, which have thicknesses at theangstrom level or can have their thicknesses controlled at that level,are well known. A thin recording medium having an optical recordingproperty can be manufactured by using an organic material with aphotoisomerization property as the molecules of the LB film. Forexample, a method of using spiropyrane derivatives (E. Ando, J. Hibino,T. Hashida and K. Morimoto, Thin Solid Films, 160, 279 (1988)), and amethod of applying azobenzene derivatives (H. S. Blairand and C. B.McArdle, Polymer, 25, 1347 (1984)), are known in the art.

However, the use of conventional magnetic recording media usinginorganic magnetic materials has been limited since the thickness of themedia cannot be thinner than a few hundred angstroms. The conventionaloptical recording media applying photoisomerization organic materials,on the other hand, can be made thin due to the use of LB films. However,these optical recording media, which do not have sufficient enduranceagainst processing, cannot be put to practical use.

SUMMARY OF THE INVENTION

Objectives of the invention are to provide an information recordingmedium which has a thickness of a few or dozens of angstroms or can haveits thickness controlled at that angstrom level, with excellentstability and endurance against processing; a method of manufacturingthe same; and methods of recording, reading and erasing information onthe medium.

In order to accomplish the above objectives, the first informationrecording medium of the invention comprises an information recordinglayer comprising a dicyclopentadiene skeleton on a substrate; the ringof the dicyclopentadiene skeleton is selectively opened by heat orlight, thus recording information by forming cyclopentadiene skeletons.

The second information recording medium of the invention also comprisesan information recording layer comprising a dicyclopentadiene skeletonon a substrate; a metal ion is incorporated into the selectively openedsection of the ring of the dicyclopentadiene skeleton, thereby recordinginformation by forming a metallocene skeleton.

The third information recording medium of the invention comprises aninformation recording layer comprising ring-skeletons on a substrate; ametal ion is selectively incorporated between at least tworing-skeletons, thus recording information by forming a metalloceneskeleton or a skeleton analogous to the metallocene skeleton.

In the above-noted composition, the skeleton analogous to themetallocene skeleton can be formed, for instance, by incorporating achromium ion between benzene rings.

In the above-noted composition, it is preferable that the ring-skeletonis a cyclopentadiene skeleton, a heterocycle or a benzene ring.

In the above-noted composition, it is preferable that the informationrecording layer is directly or indirectly chemically bonded to thesubstrate surface via at least one atom selected from the groupconsisting of C, Si, Ge, Sn, Ti, Zr and S.

In the above-noted composition, it is preferable that the informationrecording layer is a monomolecular film, a monomolecular multilayer filmor a polymer film.

A method of manufacturing an information recording medium of theinvention includes the steps of:

preparing a molecule which includes at least one functional groupselected from the group consisting of a functional group of Formula 1, afunctional group of Formula 2, a halogenated sulfonyl group of Formula3, a halogenated sulfinyl group of Formula 4 and a cyano group (--CN),and also includes ring-skeletons;

contacting and reacting the molecule to a substrate having an activehydrogen or an alkali metal on its surface, thus fixing the molecule tothe substrate surface via a covalent bond.

Formula 1 ##STR1##

(wherein A represents C, Si, Ge, Sn, Ti or Zr; and X represents ahalogen, an isocyanate group, a cyano group or an alkoxyl group)

Formula 2 ##STR2##

(wherein A' represents N or O)

Formula 3 ##STR3##

(wherein X represents a halogen)

Formula 4 ##STR4##

(wherein X represents a halogen)

In the above-noted composition, it is preferable that the ring-skeletonis a dicyclopentadiene skeleton, a cyclopentadiene skeleton, aheterocycle or a benzene ring.

In the above-noted composition, it is preferable that the informationrecording layer is a monomolecular film, a monomolecular multilayer filmor a polymer film.

The first method of using the information recording medium of theinvention to record information in an information recording layer on asubstrate, includes the step of:

selectively opening the ring of a dicyclopentadiene skeleton in theinformation recording layer by heat or light, thereby recordinginformation by forming cyclopentadiene skeletons.

The second method of using the information recording medium of theinvention to record information in an information recording layer on asubstrate, includes the steps of:

selectively opening the ring of a dicyclopentadiene skeleton in theinformation recording layer by heat or light:

eliminating a cyclopentadiene proton from the skeleton, thus creating acyclopentadienide ion; and

incorporating a metal ion into the cyclopentadienide ion, therebyrecording information by forming a metallocene skeleton.

The third method of using the information recording medium of theinvention involves incorporating a metal ion between at least tworing-skeletons, thus recording information by forming a metalloceneskeleton or a skeleton analogous to the metallocene skeleton.

In the above-noted composition, it is preferable that the ring-skeletonis a cyclopentadiene skeleton, a heterocycle and a benzene ring.

In the second and third methods of the invention, multiple storageand/or many valued memory can be carried out by repeating the recordingprocedure mentioned above while changing the kind of metal ion for eachrepetition.

In the first and second methods of the invention, it is preferable thatthe ring of the dicyclopentadiene skeleton is selectively opened by ascanning probe electron microscope.

In this invention, it is preferable that information is read bydetecting the differences in the light absorption and refractive indexvalues of a dicyclopentadiene skeleton from the values of acyclopentadiene skeleton.

In this invention, it is also preferable that information is read bydetecting the differences in the light absorption and refractive indexvalues of a dicyclopentadiene skeleton, a cyclopentadiene skeleton, aheterocycle or a benzene ring from the values of a metallocene skeleton,a skeleton analogous to the metallocene skeleton or a metal atom.

In this invention, it is further preferable that the metalloceneskeleton, the skeleton analogous to the metallocene skeleton or themetal atom is recognized by a scanning probe electron microscope or anelectron beam.

In the above-noted methods of using an information recording medium ofthe invention, the information recorded in the information recordingmedium can be erased by removing a section comprising the metalloceneskeleton or the skeleton analogous to the metallocene skeleton producedwhen information is recorded.

The information recording medium of the invention comprises a strongultrathin information recording layer directly or indirectly covalentlybonded to a substrate; such a medium was never realized until now. It ispossible with this invention to provide an information recording layerwhich has a thickness at the angstrom level or can have its thicknesscontrolled at that level.

The first method of the invention for recording information onto aninformation recording medium of the invention comprises:

forming an information recording layer comprising a dicyclopentadieneskeleton on a substrate;

selectively opening the ring of the dicyclopentadiene skeleton, thusforming cyclopentadiene skeletons and recording information.

The information recorded in the information recording medium by thefirst method can be read by detecting the differences in the lightabsorption or refractive index values of a dicyclopentadiene skeletonfrom the values of a cyclopentadiene skeleton.

The second method of the invention for recording information onto aninformation recording medium of the invention comprises:

forming an information recording layer comprising a dicyclopentadieneskeleton on a substrate;

selectively opening the ring of the dicylopentadiene skeleton andincorporating a metal ion into the opened section of the ring, thusrecording information by forming a metallocene skeleton.

The third method of the invention for recording information onto aninformation recording medium of the invention comprises:

forming an information recording layer comprising a cyclopentadieneskeleton, a heterocycle or a benzene ring on a substrate;

selectively incorporating a metal ion between at least two rings of thecyclopentadiene skeleton, heterocycle or benzene ring, thereby recordinginformation by forming a metallocene skeleton or a skeleton analogous tothe metallocene skeleton.

The information recorded in the information recording medium by thesecond or third method can be read by detecting the differences in thelight absorption or refractive index values of a cyclopentadieneskeleton, a dicyclopentadiene skeleton, a heterocycle or a benzene ringfrom the values of a metallocene skeleton, a skeleton analogous to themetallocene skeleton or a metal atom.

The method of the invention for erasing information includes directingthe cycloaddition of cyclopentadiene skeletons (first method), cleavinga metallocene skeleton or a skeleton analogous to the metalloceneskeleton (second method) and eliminating a section comprising ametallocene skeleton or a skeleton analogous to the metallocene skeleton(third method). In the second method, it is appropriate to carry out areductive cleavage by bases, thus eliminating only a metal atom andleaving a cyclopentadiene skeleton for another recording. In the thirdmethod, however, another recording cannot be made in the same placesince the section comprising the metallocene skeleton or the skeletonanalogous to the metallocene skeleton is removed by the method.

A dicyclopentadiene skeleton is formed by the cycloaddition of twoneighbouring cyclopentadienes through a Diels-Alder reaction. Theskeleton is stable at room temperature. Either a dicyclopentadienederivative or a cyclopentadiene derivative can be used as a startingmaterial for the information recording layer. Then, through theabove-mentioned cycloaddition process, an information recording layercomprising the dicyclopentadiene skeleton is formed.

Preferably, either heat or light is used for opening the ring of thedicyclopentadiene skeleton. As a heat or light source, it is preferableto use a semiconductor laser or the like which provides a small beamdiameter and provides high energy. The semiconductor laser can also beuseful for the readout of information.

By using a scanning probe electron microscope for the ring-opening ofthe dicyclopentadiene skeleton and the readout of information, itbecomes possible to achieve the recording and readout of information ata molecular or atomic level.

As metal ions used for forming the metallocene skeleton or the skeletonanalogous to the metallocene skeleton, Cr, Mn, Fe, Co, Ni, Os, Ru, V orthe like are useful. However, the metal ion applicable for the inventionis not limited to the ions mentioned above. In order to impart stabilityto the metallocene skeleton, however, it is preferable to use Fe, Ru orOs.

The second and third information recording media of the invention canachieve multiple storage and/or many valued memory by repeatingrecording process. However, for each repetition, the kind of metal ionincorporated into an information recording layer should be changed. Inthe case where the information recording layer is comprised of adicyclopentadiene skeleton, the energy of heat or light should be of adegree capable of opening the ring of the dicyclopentadiene skeletonwithout breaking down the metallocene skeleton or the skeleton analogousto the metallocene skeleton. It is appropriate to make use of thedifferences in light absorption or refractive index for recognizing ordistinguishing the kind of metallocene skeleton, skeleton analogous tothe metallocene skeleton or metal ion, thereby reading information.

It is preferable to use an organic polymer film or an organic thin film,comprising a cyclopentadiene skeleton, a heterocycle, a benzene ring ora dicyclopentadiene skeleton, as the information recording layer on thesubstrate. However, the information recording layer of the invention isnot limited to the above-noted films. In case of an organic polymer filmor an organic thin film comprising a cyclopentadiene skeleton, the filmmay include an indenin derivative group, a fluorene derivative group orthe like. Moreover, when the film comprises a heterocycle or a benzenering, the film may comprise the heterocycle or the benzene ring as asection of a functional group. In taking into consideration the densityof a cyclopentadiene skeleton, a heterocycle, a benzene ring or adicyclopentadiene skeleton, and the thickness of an informationrecording layer, it is preferable to form a monomolecular film or amultilayer film with several layers as the information recording layer.Endurance, including endurance against processing, is required for aninformation recording layer after the formation of the layer; therefore,a chemically adsorbed monomolecular film or a chemically adsorbedmultilayer film is suitable for the layer. When forming a chemicallyadsorbed multilayer film as an information recording layer, the kind ofa metallocene skeleton or a skeleton analogous to the metalloceneskeleton can be differentiated for each layer. Or alternatively,different kinds of metallocene skeletons or skeletons analogous to themetallocene skeletons can be included within a layer. It is alsopossible to build up a layer comprising different kinds of metalloceneskeletons or skeletons analogous to the metallocene skeletons. As aresult, a high density recording of multiple bits in one spot can berealized.

Information recorded by the first information recording medium of theinvention can be erased by the cycloaddition of cyclopentadieneskeletons. In other words, the medium can record and erase informationwithout physically incorporating and eliminating metal ions. Therefore,the recording and erasing of information can be repeated many times bythe medium.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an enlarged sectional view of a substrate of Example 1prior to application of the recording layer.

FIG. 2 shows an enlarged sectional view of a chemically adsorbedmonomolecular film of Example 1.

FIG. 3 shows an enlarged sectional view of another chemically adsorbedmonomolecular film of Example 1.

FIG. 4 shows an enlarged sectional view of a chemically adsorbedmonomolecular film of Example 2.

FIG. 5 shows an enlarged sectional view of a chemically adsorbedmonomolecular film of Example 4.

FIG. 6 shows an enlarged sectional view of another chemically adsorbedmonomolecular film of Example 4.

FIG. 7 shows an enlarged sectional view of a further chemically adsorbedmonomolecular film of Example 4.

FIG. 8 shows an enlarged sectional view of a chemically adsorbedmonomolecular film of Example 5.

FIG. 9 shows an enlarged sectional view of another chemically adsorbedmonomolecular film of Example 5.

FIG. 10 shows an enlarged sectional view of a further chemicallyadsorbed multilayer film of Example 5.

FIG. 11 shows an enlarged sectional view of yet another chemicallyadsorbed multilayer film of Example 5.

FIG. 12 shows an enlarged sectional view of a chemically adsorbedmonomolecular film of Example 6.

FIG. 13 shows an enlarged sectional view of a chemically adsorbedmonomolecular film of Example 7.

FIG. 14 shows an enlarged sectional view of another chemically adsorbedmonomolecular film of Example 7.

FIG. 15 shows an enlarged sectional view of a chemically adsorbedmonomolecular film of Example 8.

FIG. 16 shows an enlarged sectional view of another chemically adsorbedmonomolecular film of Example 8 after being irradiated with a laser.

DETAILED DESCRIPTION OF THE INVENTION

The invention is specifically described by referring to the followingexamples.

Basic chemical adsorption methods include the procedure mentioned, forexample, in J. Sagiv, Journal of American Chemical Society, 102:92(1980) and in K. Ogawa et al., Langmuir, 6:851 (1990). In these methods,a chemically adsorbed film is manufactured by a dehydrochlorinationreaction of molecules comprising chlorosilyl groups (chemical adsorbent)to a substrate surface comprising hydroxyl groups or the like, thusfixing the groups to the substrate surface via covalent bonds.

In forming a chemically adsorbed film, a functional group, which bonds amolecule to a substrate, is at least one functional group selected fromthe group consisting of a functional group of Formula 1 set forth above,a functional group of Formula 2 set forth above, a halogenated sulfonylgroup of Formula 3 set forth above, a halogenated sulfinyl group ofFormula 4 set forth above and a cyano group (--CN). However, thefunctional group applicable to the invention is not limited to theabove-noted groups. As a halogen of the invention, Cl, Br or I can beincluded. In terms of reactivity, however, it is preferable to use Cl.

The substrates useful in this invention have on the surface at least onefunctional group selected from the group consisting of a hydroxyl group,a carboxyl group, a sulfonic acid group, a sulfinic acid group, aphosphoric acid group, a phosphorous acid group, a quaternary Ammoniumgroup, a quaternary phosphonium group, a thiol group and an amino group;and/or at least one functional group, in which an alkali metal oralkaline earth metal is substituted for H of the group, selected fromthe group consisting of a hydroxyl group, a carboxyl group, a sulfonicacid group, a sulfinic acid group, a phosphoric acid group, aphosphorous acid group, a quaternary ammonium group, a quaternaryphosphonium group, a thiol group and an amino group. The chemicallyadsorbed film of the invention is not limited to films which include theabove-mentioned functional groups, and is fixed to the substrate surfacecomprising the functional group.

When the substrate surface has none or only a few of the functionalgroups mentioned above, a UV irradiation or oxidizing agent treatmentshould be applied to the surface, thus effectively creating orincreasing the functional groups on the surface.

The method of fixing the chemically adsorbed film to the substratesurface includes but is not limited to methods of contacting a substrateto a liquid and/or gaseous chemical adsorbent, and/or to a solutiondissolving the chemical adsorbent.

In the case of using the above-mentioned solution dissolving thechemical adsorbent, it is preferable to use a solvent comprised ofmolecules with no active hydrogens. For instance, if the chemicaladsorbent comprises long-chain alkyl groups, a mixed solvent ofhydrocarbon and halogenated hydrocarbon can be employed. In addition, itis appropriate to use halogenated hydrocarbon solvent, aromatic solventor the like for the chemical adsorbent comprising carbonyl groups.However, the solvent applicable in the invention is not limited to thesolvents mentioned above.

After fixing the chemically adsorbed film to the substrate, it ispreferable to remove unreacted molecules: as a result, a monomolecularfilm and a multilayer film can be easily formed on the substrate. It ispreferable to use an aprotic solvent to remove the unreacted molecules;for instance, halogenated carbon, ether, lactone, ester, nitrile, amideor the like are included as such solvents. However, the solvent is notlimited to those solvents.

The invention will now be explained specifically in the followingexamples.

EXAMPLE 1

An adsorption solution A was prepared by dissolving about 1% by weightof (3-dicyclopentadienylpropyl)trichlorosilane into a mixed solvent ofhexadecane, carbon tetrachloride and chloroform at a weight ratio of80:12:8, respectively.

A glass substrate 1 (hydrophilic substrate) as shown in FIG. 1 wasprepared. After being washed with an organic solvent, glass substrate 1was dipped and held in adsorption solution A for three hours. Due tothis treatment, bonds of the following Formula 5 were formed on glasssubstrate 1.

Formula 5 ##STR5##

(wherein C₁₀ H₁₁ represents a dicyclopentadienyl group)

After washing glass substrate 1 with chloroform (nonaqueous solvent) for15 minutes and with water for another 15 minutes, a chemically adsorbedmonomolecular film 2 of FIG. 2 was formed on the substrate surface.Chemically adsorbed monomolecular film 2 was firmly bonded to glasssubstrate 1, and had excellent water-repelling properties.

The formation of the film was confirmed by obtaining particular signalsfor this structure at 2925, 2855 (attribute of --CH₂ --), 1650(attribute of C═C), 1465 (attribute of --CH₂ --), and 1080 (attribute ofSi-O)cm⁻¹ by Fourier transform infrared absorption spectral (FTIR)measurement.

Then, glass substrate 1 formed with chemically adsorbed monomolecularfilm 2 was dipped and held in decalin. After heating a section of thefilm with an infrared laser at around 190° C. for one hour, NaH and thenanhydrous FeCl₂ were added to the decalin.

After the above-noted procedure, glass substrate 1 was washed withhexane for 10 minutes and then with water for another 10 minutes; as aresult, the skeleton, which had been irradiated with the infrared laser,was changed to a ferrocene skeleton, thus forming a chemically adsorbedmonomolecular film 3 (FIG. 3). Chemically adsorbed monomolecular film 3was firmly connected to the substrate and had excellent water-repellingproperties.

The creation of an additional particular signal at 815 (attribute of aferrocene skeleton) cm⁻¹ and also the disappearance of the signal at1650 cm⁻¹ were confirmed by FTIR measurement. Chemically adsorbedmonomolecular 3 was proved to have Fe atoms by X-ray photoelectricspectroscopic (XPS) measurement. The above-noted results indicate that asignal can be recorded as a ferrocene in the section irradiated with thelaser.

EXAMPLE 2

Glass substrate 1 formed with chemically adsorbed monomolecular film 3of Example 1 was dipped and held in decalin. After heating only thedicyclopentadiene skeleton, which had not been changed to the ferroceneskeleton, with an infrared laser at about 190° C. for one hour, NaH andthen anhydrous RuCl₂ were added to the decalin.

After that, glass substrate 1 was washed with hexane for 10 minutes andthen with water for another 10 minutes, thereby forming a chemicallyadsorbed monomolecular film 4, in which a ferrocene skeleton and aruthenocene skeleton are intermingled, as shown in FIG. 4. Themonomolecular film was firmly connected to the substrate, and possessedgood water-repelling properties.

The creation of an additional signal at 821 cm⁻¹ was confirmed by FTIRmeasurement. In addition to the Fe atom, a Ru atom was also found inchemically adsorbed monomolecular film 4 by XPS measurement. The resultsindicate that the information recorded with light of 821 cm⁻¹ and 815cm⁻¹ can be recognized and read.

EXAMPLE 3

The surface of chemically adsorbed monomolecular film 4 includingferrocene and ruthenocene was observed in ethanol with an interatomicforce microscope (AFM), a type of scanning probe electron microscope. Inobserving the sections of the film which had been irradiated with theinfrared laser in Examples 1 and 2, convex and concave surfaces withthree different heights were clearly found. In other words, there weretwo kinds of metallocene skeletons which had been formed as a result ofthe above-described reactions, and an unreacted dicyclopentadieneskeleton in chemically adsorbed monomolecular film 4.

EXAMPLE 4

An adsorption solution B was prepared by dissolving about 1% by weightof 14-iodotetradecyltrichlorosilane into a mixed solvent of hexadecane,carbon tetrachloride and chloroform at a weight ratio of 80:12:8,respectively.

As shown in FIG. 1, a glass substrate 1 was used as a hydrophilicsubstrate. After washing glass substrate 1 with an organic solvent, thesubstrate was dipped and held in adsorption solution B for three hours.Due to this treatment, bonds of the following Formula 6 were formed onglass substrate 1.

Formula 6 ##STR6##

Glass substrate 1 was washed with chloroform (nonaqueous solvent) for 15minutes and then with water for another 15 minutes, thus forming achemically adsorbed monomolecular film 5. The monomolecular film wasfirmly connected to the substrate, and possessed good water-repellingproperties.

Signals were obtained for this structure at 2925, 2855 (attribute of--CH₂ --), 1465 (attribute of --CH₂ --), and 1080 (attribute of Si-O)cm⁻¹ by FTIR measurement, thereby confirming the formation of the film.

Glass substrate 1 formed with chemically adsorbed monomolecular film 5was dipped and held in dry tetrahydrofuran (THF) under a nitrogenatmosphere. Hexapentadienide sodium was then added and reacted for 30minutes, thus forming cyclopentadiene skeletons. Dicyclopentadieneskeletons were soon formed by the cycloaddition of two neighboringcyclopentadiene skeletons, thus forming a chemically adsorbedmonomolecular film 6 as shown in FIG. 6.

An additional signal was obtained for this structure at 1650 (attributeof C═C) cm⁻¹ by FTIR measurement, thereby confirming the formation ofthe film. In other words, the information recorded with light of 1650cm⁻¹ can be read.

Glass substrate 1 having chemically adsorbed monomolecular film 6 on itssurface was dipped and held in decalin. After heating only one sectionof the film with an infrared laser at about 190° C. for one hour, NaHand then anhydrous FeCl₂ were added to the decalin.

After that, glass substrate 1 was washed with hexane for 10 minutes andthen with water for another 10 minutes. As a result, the chemicallyadsorbed monomolecular film 7 of FIG. 7, in which only the sectionirradiated with the infrared laser was changed to a ferrocene skeleton,was formed. The monomolecular film was firmly connected to thesubstrate, and possessed good water-repelling properties.

A particular signal was obtained for this structure at 815 (attribute ofa ferrocene skeleton) cm⁻¹ by FTIR measurement. According to XPSmeasurement, it was proved that chemically adsorbed monomolecular film 7comprised Fe atoms. These results indicate the information recorded withlight of 815 cm⁻¹ can be read.

EXAMPLE 5

An adsorption solution C was prepared by dissolving about 1% by weightof 6-dicyclopentadienyl-1,8-di(trichlorosilyl)octane into a mixedsolvent of hexadecane, carbon tetrachloride and chloroform at a weightratio of 80:12:8, respectively.

As shown in FIG. 1, a glass substrate 1 was used as a hydrophilicsubstrate. After being washed with organic solvent, glass substrate 1was dipped and held in adsorption solution C for three hours. As aresult, bonds of the following Formula 7 were formed on glass substrate1.

Formula 7 ##STR7##

(wherein C₁₀ H₁₁ represents a dicyclopentadienyl skeleton)

Glass substrate 1 was washed with chloroform for 15 minutes and thenwith water for another 15 minutes, thus forming a chemically adsorbedmonomolecular film 8 as shown in FIG. 8. The monomolecular film wasfirmly connected to the substrate, and possessed good water-repellingproperties.

Distinctive signals were obtained for this structure at 2925, 2855(attribute of --CH₂ --), 1650 (attribute of C═C), 1465 (attribute of--CH₂ --), 1080 (attribute of Si-O) cm by FTIR measurement, thusconfirming formation of the film.

Glass substrate 1 formed with chemically adsorbed monomolecular film 8was dipped and held in decalin, and only a section of the film washeated with an infrared laser at about 190° C. for one hour. NaH andthen FeCl₂ were added to the decalin.

Glass substrate 1, moreover, was washed with hexane for 10 minutes andthen with water for another 10 minutes. As shown in FIG. 9, a chemicallyadsorbed monomolecular film 9 comprising a ferrocene skeleton wasformed. The monomolecular film was firmly connected to the substrate,and possessed good water-repelling properties.

An additional distinctive signal for this structure at 815 (attribute ofa ferrocene skeleton) cm⁻¹ was confirmed by FTIR measurement while thesignal at 1650 cm⁻¹ disappeared. According to XPS measurement, it wasconfirmed that the film comprised Fe atoms, thus indicating theformation of a ferrocene skeleton.

Glass substrate 1 having chemically adsorbed monomolecular film 9 on itssurface was then dipped and held in adsorption solution C for threehours. After washing glass substrate 1, a chemically adsorbedmonomolecular film 10 was formed, thus forming a chemically adsorbedmultilayer film of FIG. 10 on the substrate. The monomolecular film wasfirmly connected to the substrate, and possessed good water-repellingproperties.

The signals obtained by FTIR measurement at 2925, 2855 (attribute of--CH₂ --), 1465 (attribute of --CH₂ --), 1080 (attribute of Si-O) cm⁻¹were doubled, thus confirming the formation of the multilayer film.

Glass substrate 1, which had the .chemically adsorbed multilayer filmcomprised of chemically adsorbed monomolecular films 9 and 10 on itssurface, was dipped and held in decalin. Then, a section of chemicallyadsorbed monomolecular film 10 was heated with an infrared laser atabout 190° C. for one hour. NaH and then RuCl₂ were added to thedecalin.

After washing glass substrate 1 with hexane for 10 minutes and then withwater for another 10 minutes, a chemically adsorbed monomolecular film11 comprising ruthenocene skeletons was formed as shown in FIG. 11. Themonomolecular film was firmly connected to the substrate, and possessedgood water-repelling properties.

An additional distinctive signal was found at 821 (attribute of aruthenocene skeleton) cm⁻¹ by FTIR measurement while the signal at 1650cm⁻¹ disappeared. It was confirmed by XPS measurement that chemicallyadsorbed monomolecular film 11 comprised Ru atoms, thus indicating theformation of ruthenocene skeletons. According to the above-notedresults, the information recorded with light of 821 cm⁻¹ and 815 cm⁻¹can be read.

EXAMPLE 6

Glass substrate 1 having chemically adsorbed monomolecular film 7 ofExample 4 on its surface was dipped and held in frozen methylenechloride. Ethylamine was then added to the solution. After threeminutes, lithium powder was also added to the methylene chloride, andthen glass substrate 1 was left for an extra 10, minutes. After beingquenched with methanol, glass substrate 1 was washed with chloroform for10 minutes and then with water for another 10 minutes. As a result, achemically adsorbed monomolecular film 12 was formed as shown in FIG.12. The monomolecular film was firmly connected to the substrate, andpossessed good water-repelling properties.

FTIR measurement showed that the signal at 815 cm⁻¹ dissapeared. XPSmeasurement, in addition, showed that chemically adsorbed monomolecularfilm 12 did not comprise Fe atoms, thereby confirming the disappearanceof ferrocene skeletons in the film. In other words, both readout anderasure of recorded information can be achieved with light of 815 cm⁻¹in the invention.

EXAMPLE 7

An adsorption solution D was prepared by dissolving about 1% by weightof (3-cyclopentadienyl propyl)trichlorosilane into a mixed solvent ofhexadecane, carbon tetrachloride and chloroform at a weight ratio of80:12:8, respectively,

As shown in FIG. 1, a glass substrate 1 was used as a hydrophilicsubstrate. After being washed with organic solvent, glass substrate 1was dipped and held in adsorption solution D for three hours. As aresult, bonds of the following formula 8 were formed on glass substrate,

Formula 8 ##STR8##

(wherein C₅ H₅ represents a cyclopentadienyl group)

Glass substrate 1 was first washed: with chloroform for 15 minutes andthen with water for another 15 minutes, thus forming a chemicallyadsorbed monomolecular film 13 as shown in FIG. 13. The monomolecularfilm was firmly connected to the substrate, and possessed goodwater-repelling properties.

Distinctive signals were obtained for this structure at 2925, 2855(attribute of --CH₂ --). 1850 (attribute of C═C), 1485 (attribute of--CH₂ --) and 1080 (attribute of Si-O) cm⁻¹ by FTIR measurement, therebyconfirming the formation of the film.

Glass substrate 1 having chemically adsorbed monomolecular film 13 onits surface was dipped and held in decalin. NaH and then anhydrous FeCl₂were added to the decalin.

Thereafter, glass substrate 1 was washed with hexane for 10 minutes andthen with water for another 10 minutes, thus forming a chemicallyadsorbed monomolecular film 14 comprising a ferrocene skeleton as shownin FIG. 14. The monomolecular film was firmly connected to thesubstrate, and possessed good water-repelling properties.

FTIR measurement showed the disappearance of the signal at 1650 cm⁻¹ andthe creation of an additional distinctive signal at 815 (attribute of aferrocene skeleton) cm⁻¹ XPS measurement indicated that chemicallyadsorbed monomolecular film 14 comprised Fe atoms. The results show thatthe information recorded with light of 815 cm⁻¹ can be read.

EXAMPLE 8

An adsorption solution E was prepared by dissolving about 1% by weightof (8-dicyclopentadienyloctyl)trichlorosilane into a mixed solvent ofhexadecane, carbon tetrachloride and chloroform at a weight ratio of80:12:8, respectively.

A glass substrate 1 (hydrophilic substrate) as shown in FIG. 1 wasprepared. After being washed with an organic solvent, glass substrate 1was dipped and held in adsorption solution E for three hours. Afterbeing washed with chloroform (nonaqeous solvent) for 15 minutes and thenwith water for another 15 minutes, glass substrate 1 was annealed at100° C. in a nitrogen atmosphere for 20 minutes. As a result, achemically adsorbed monomolecular film 15 of FIG. 15 was formed on thesubstrate surface. Chemically adsorbed monomolecular film 15 was firmlybonded to glass substrate 1, and had excellent water-repellingproperties. The formation of the film was confirmed by obtainingparticular signals for this structure at 2925, 2855 (attribute of --CH₂--), 1650 (attribute of C═C), 1465 (attribute of --CH₂ --), and 1080(attribute of Si-O)cm⁻¹ by FTIR measurement.

The half of glass substrate 1 formed with chemically adsorbedmonomolecular film 15 was then irradiated with an infrared laser atabout 190° C. for five minutes. Signals attributed to the vibration ofthe aromatic skeleton were found at 1660 and 1610 cm⁻¹ by FTIRmeasurement, and the measurement also showed that the signal at 1650cm⁻¹ decreased to 45% of the signal obtained immediately after theformation of chemically adsorbed monomolecular film 15. These resultsindicate that the rings of dicyclopentadiene skeletons were opened bythe irradiation, and that cyclopentadiene skeletons were formed. Inother words, a chemically adsorbed monomolecular film 16 of FIG. 16 wasformed on the surface of glass substrate 1. The signals from glasssubstrate 1 were observed by FTIR measurement after 5, 10, 30 and 60days, but there was no sign of a change in the signals.

Following that, glass substrate 1 was again irradiated with an infraredlaser at 70° C. for two minutes. According to FTIR measurement, thesignals at 1660 and 1610 cm⁻¹ disappeared, and the intensity of thesignal at 1650 cm⁻¹ returned to the same intensity of the initial signalobtained immediately after the formation of chemically adsorbedmonomolecular film 15, thereby confirming the formation ofdicyclopentadiene skeletons.

Even when functional groups other than the ones used in Examples 1-8were applied, similar information recording layers were formed.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The embodimentsdisclosed in this application are to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are intended to be embraced therein.

We claim:
 1. A method of recording information on an informationrecording medium, which is comprised of an information recording layercomprising a dicyclopentadiene skeleton on a substrate surface,comprising:selectively opening the ring of said dicyclopentadieneskeleton in said information recording layer by heat or light, thusrecording information by forming cyclopentadiene skeletons.
 2. A methodof recording information on an information recording medium, which iscomprised of an information recording layer comprising adicyclopentadiene skeleton on a substrate surface,comprising:selectively opening the ring of said dicyclopentadieneskeleton in said information recording layer by heat or light;eliminating a cyclopentadiene proton from said dicyclopentadieneskeleton, thus creating a cyclopentadienide ion; and incorporating ametal ion into said cyclopentadienide ion, thereby recording informationby forming a metallocene skeleton.
 3. A method according to claim 2,wherein multiple storage or many valued memory is carried out byrepeating the recording of information while changing the kind of saidmetal ion for each repetition.
 4. A method of recording information onan information recording medium, which is comprised of an informationrecording layer comprising a cyclopentadiene skeleton, a heterocycle ora benzene ring on a substrate surface, comprising:incorporating a metalion between at least two rings of the cyclopentadiene skeleton,heterocycle or benzene ring, thus recording information by forming ametallocene skeleton or a skeleton analogous to said metalloceneskeleton.
 5. A method according to claim 4, wherein multiple storage ormany valued memory is carried out by repeating the recording ofinformation while changing the kind of said metal ion for eachrepetition.
 6. A method for reading information recorded on aninformation recording medium, said information being recorded by theformation of cyclopentadiene skeletons in the information recordingmedium, said method comprising detecting in the medium differences inlight absorption or refractive index between the light absorption orrefractive index of a dicyclopentadiene skeleton and the lightabsorption or refractive index of said cyclopentadiene skeleton.
 7. Amethod according to claim 6, wherein said dicyclopentadiene skeleton orsaid cyclopentadiene skeleton is recognized by a scanning probe electronmicroscope or an electron beam.
 8. A method for reading informationrecorded on an information recording medium, said information beingrecorded by the formation of a metallocene skeleton or a skeletonanalogous to said metallocene skeleton in the information recordingmedium, said method comprising detecting in the medium differences inlight absorption or refractive index between the light absorption orrefractive index of a ring-skeleton in said medium selected from thegroup consisting of a dicyclopentadiene skeleton, a cyclopentadieneskeleton, a heterocycle and a benzene ring, and the light absorption orrefractive index of said metallocene skeleton, said skeleton analogousto said metallocene skeleton or a metal ion.
 9. A method according toclaim 8, wherein said metallocene skeleton, said skeleton analogous tosaid metallocene skeleton or said metal atom is recognized by a scanningprobe electron microscope or an electron beam.
 10. A method of erasinginformation recorded on an information recording medium, whereininformation recorded in said information recording medium by theselective formation of cyclopentadiene skeletons is erased by thecycloaddition of said cyclopentadiene skeletons.
 11. A method of erasinginformation recorded on an information recording medium, whereininformation recorded in said information recording medium by theselective formation of a metallocene skeleton or a skeleton analogous tosaid metallocene skeleton is erased by cleaving said metalloceneskeleton or said skeleton analogous to said metallocene skeleton.
 12. Amethod of erasing information recorded on an information recordingmedium, wherein information recorded in said information recordingmedium by the selective formation of a metallocene skeleton or askeleton analogous to a metallocene skeleton is erased by removing asection of the medium including said metallocene skeleton or saidskeleton analogous to said metallocene skeleton.
 13. A method ofrecording information on an information recording medium, whichcomprises an information recording layer comprising a dicyclopentadieneskeleton on a substrate surface, comprising:selectively opening the ringof said dicyclopentadiene skeleton by a scanning probe electronmicroscope, thus recording information by forming cyclopentadieneskeletons.
 14. A method of recording information on an informationrecording medium, comprising an information recording layer comprising adicyclopentadiene skeleton on a substrate surface,comprising:selectively opening the ring of said dicyclopentadieneskeleton in said information recording layer by a scanning probeelectron microscope; eliminating a cyclopentadiene proton from saiddicyclopentadiene skeleton, thus creating a cyclopentadienide ion; andincorporating a metal ion into said cyclopentadienide ion, therebyrecording information by forming a metallocene skeleton.